1. Field of the Invention
The present invention relates to the field of semiconductor processing and more specifically to a device feature layout and a method of generating the same for improved chemical mechanical polishing.
2. Discussion of Related Art
As device dimensions continue to shrink modern integrated circuits now contain more and more levels of features. For example, modern high density circuits, which can contain literally tens of millions of transistors formed in a silicon monocrystalline substrate, require over six levels of metalization to electrically couple the transistors into functional circuits. Similarly, novel three-dimensional memory arrays such as described in co-pending U.S. patent application Ser. No. 09/560,626, filed Apr. 28, 2000, and entitled Three-Dimensional Memory Array and Method of Fabrication can utilize over nine levels of silicon rails or lines. As more and more levels of features are added to integrated circuits, the planarization of each level is essential to enable the uniform processing of subsequent levels of features. In the past, dummy features (i.e., electrically isolated inactive features) have been locally inserted between active features of a level in order enhance the chemical mechanical planarization of that level. Unfortunately, however, such techniques of “dummification” (i.e., adding dummy features locally between active features) do not take into consideration the size and density of the active features. Present dummification techniques are useful for providing uniform local planarization, however, they fail to provide mid-range planarity. Lack of mid-range planarity can cause photolithography exposure systems used to form photoresist mask for subsequent layers to print inaccurate images, thereby preventing the formation of additional levels of features.
Thus, what is desired is a method of sizing and locating dummy features in an integrated circuit device level to improve the mid-range planarity of a chemical mechanical polishing process.